Proximal humeral fractures represent about 4-5% of all fractures and represent the third most common fracture among older patients. In many patients, the proximal humeral fracture most typically results from a fall. The damage to the humerus can be compounded by osteoporosis or an otherwise weakened bone that is found more frequently in older female patients. In younger patients, proximal humeral fractures are more likely to be a result of high-energy trauma; such as an automobile accident or a sporting injury.
The majority of proximal humeral fractures are minimally or non-displaced and are generally treated non-operatively.
However, operative fixation is indicated in displaced, angulated and rotated fracture patterns. Among the operative solutions commonly used for fixation are: (1) osteosuture and tension band technologies; (2) percutaneous fixation using pins and wires; (3) rigid intramedullary nailing (e.g., using a large rod inside the bone); (4) plate osteosynthesis (e.g., using open reduction internal fixation using plate(s) and screws); (5) arthroplasty (e.g. using a prosthesis to replace a broken portion of a humerus); and, other indication-specific techniques.
There are two primary categories for surgical fixation: (1) a device that is within the skin (internal fixation); and (2) a device that extends out of the skin (external fixation). There are two common types of internal fixation approaches for long bone surgery: (a) a plate that is screwed to the outside of the bone; or (b) a rod that goes down the center of the bone.
Current plate technology uses straight, also referred to as linear, plates, as illustrated in FIG. 1B. For example, U.S. Pat. No. 6,096,040, issued to Esser, on Aug. 1, 2000, claims a linear bone plate. Additional examples of current proximal humeral plates are the Stryker AxSOS Locking Plating System, produced by Stryker Trauma AG at least as early as 2011. The Zimmer Periarticular Locking Plate, produced by Zimmer at least as early as 2006 are both examples of currently available linear plating systems. These straight plates limit the trajectory of the screws within the humeral head, which has been found to be problematic.
As illustrated in FIG. 1A, a humerus H is part of a human skeleton S. FIG. 1B illustrates a current linear bone plate. FIG. 2 illustrates the humerus H separated from skeleton S. The shaft of a long bone, such as the humerus H, is typically classified as the diaphysis. The end of such a bone is typically classified as the epiphysis. Bone that is transitional between the midshaft and the end is typically classified as the metaphysis.
Metaphysis and epiphysis bone are softer and more porous. The bone of the metaphysics and epiphysis is less dense than the diaphysial bone of the shaft. Since metaphysical and epiphyseal bone are cancellous bone, they are more affected by osteoporosis. Repair of metaphysis and epiphysis fractures are often complicated by their proximity to a joint. Due to the bone quality and anatomic shapes of the metaphyseal and epiphyseal bone, fixation of plates and screws in these areas is typically more difficult than fixation of plates and screws in diaphysis shaft. This may be especially true if the patient is elderly and suffers from osteoporosis. Thus, proper placement of screws in epiphysis and metaphysis bone is desirable to obtain appropriate fixation of a plate. Phrased differently, a current linear plate may obtain good fixation to the diaphysis, but fail to obtain appropriate fixation to the epiphysis and metaphysis.
While not every proximal humeral fracture is the same, the Neer system of proximal humeral fractures is based on four parts of the humerus. The four parts are as follows:    (I) fracture of the greater tuberosity:    (II) fracture of the lesser tuberosity;    (III) fracture of the humeral head; and,    (IV) fracture of the neck.
According to Neer, a fracture is displaced when there is more than 1 cm (one centimeter) of displacement and/or 45° of angulation of any one fragment with respect to the others.
Two-part fractures involve any of the 4 parts and include 1 fragment that is displaced. Three-part fractures include a displaced fracture of the surgical neck in addition to either a displaced greater tuberosity or lesser tuberosity fracture. Four-part fractures include displaced fractures of the surgical neck and both tuberosities.
FIG. 3 is a chart of the Neer system of classifying displaced proximal humeral fractures. Fractures of the proximal humerus typically follow these fracture lines. With this said, humerus H can fracture in patterns not illustrated in FIG. 3 and the Neer system is merely a way of classifying fractures. For example, humerus H may suffer complex fractures that extend into the shaft, both above and below the deltoid insertion. The Neer system may be thought of as helping surgeons to identify patients that likely would benefit from surgery. It does not determine the type of surgical intervention that might be medically beneficial.
Currently, surgeons find it problematic to use existing linear proximal plates to resolve these issues. If a surgeon has identifies a fracture that meets the indications for surgery then one of the options noted above could be used. If a surgeon selects Open-Reduction Internal Fixation (ORIF), a surgical plate could be medically beneficial.
FIG. 4 illustrates X-rays of a current linear plate fixed to a patient's humerus. FIG. 4 further illustrates the linearality of the current plates. Use of the current linear plate will produce sub-optimal screw trajectory within the humeral head. If the surgeon attempts to position the distal section of the current linear plate sufficiently anterior to avoid the deltoid tuberosity, the proximal head of the plate will be correspondingly moved anterior. This de-optimizes screw trajectory within the humeral head. Obviously, poor screw placement, likely results in sub-optimal fixation of the current linear plate to the humerus H, and particularly to the head of humerus H. Phrased differently, and as illustrated in FIG. 4, the screws fixing current linear plates to the humeral bead obtain less purchase than is optimal. Screw trajectories that pass through more bone are generally thought to obtain better purchase, also referred to as fixation, to the bone, including bone of the humeral head. Generally speaking because of the shape of the humeral head, screw trajectories through the humeral head are preferred to be in the lateral to medial orientation to optimize fixation of the plate and screws. With current plates, to avoid disruption of the deltoid insertion and the deltoid tuberosity, the plate is placed more anterior than is optimal. As the plate is placed more anteriorly, the screws are more in the posterior surface of the humerus. This results in the screws in the humeral head being oblique, and results in screws that don't obtain appropriate fixation in the anterior portion of the humeral head.
Current linear plates have various issues. First, installation of the current linear plates can require significant removal of the deltoid tuberosity and detachment of the deltoid. Second, not ail fractures will heal. If the fracture is treated with open reduction internal fixation with a plate, and the bone fails to heal appropriately, then a reverse total shoulder arthroplasty may be the appropriate treatment. A reverse total shoulder arthroplasty employs the intact function of the deltoid. Detachment of the deltoid can preclude use of a reverse total shoulder arthroplasty, in the event of the failure of surgery using the current plate to appropriately resolve the fracture of the humerus because of the fracture failing to heal. Third, and as discussed above, if the surgeon attempts to position the distal section of the current linear plate sufficiently anterior to avoid the deltoid tuberosity, the proximal head of the plate will be correspondingly moved anteriorly. This de-optimizes screw trajectory within the humeral head. Poor screw placement likely results in sub-optimal fixation of the current, linear plate to the humerus, and particularly to the head of humerus. Fourth, current plates typically have screw trajectories that run obliquely thought the humeral head from anterolateral to postromedial, rather than the more optimal true lateral to medial within the head. Current plates have all of the screw trajectories in essentially a single plane. Screw trajectories in more than one plane will provide greater strength and improved plate fixation.
Current plates are linear, and only provide fixation in essentially a single plane. When current plates are placed anterior to the deltoid insertion, the screws have a poor trajectory within the humeral head. With anterior plate positioning, the screw trajectory limits screw fixation in the anterior portion of the humeral head, which is sub-optimal. When the current plates are placed laterally, the plates damage the deltoid insertion, where the deltoid muscle attaches to the humerus.
The plate that is the subject of this patent application curves around the humerus where the proximal portion of the plate is on the lateral surface of the humeral head and the distal portion of the plate is on the anterior surface of the humeral shaft. The screws through the proximal portion have a true lateral to medial direction within the humeral head. This lateral to medial screw trajectory in the humeral head gives more optimal fixation by allowing screws be placed throughout the humeral head. The plate that is the subject of this patent application also has screws through the distal portion that have a trajectory in an anterior to posterior direction in the humeral shaft. The plate that is the subject of this patent application allows for the screws to obtain fixation in multiple planes. The curve of the plate allows the plate to avoid the deltoid tuberosity avoiding damage to the deltoid tendon and the deltoid insertion of the deltoid tuberosity. The curved portion also allows for oblique screws within the humeral metaphysis. The oblique metaphysis screws compliment the lateral to medial screws within the humeral head. The lateral to medial screw trajectory optimizes screw fixation within humeral head, while preserving the attachment of the deltoid muscle. In addition, the configuration allow the plate to extend down the entire length of the humerus allowing the plate to treat more complex fractures that extend into the humeral shaft without compromising the deltoid and avoiding potential damage to nerves, such as the radial nerve.